Modern processors are often heavily pipelined to increase operating frequencies and exploit parallelism. Data from successive stages is often stored or latched to provide inputs to the next pipeline stage. As fabrication processes improve over time, the size of storage elements decreases making them more susceptible to soft errors. Soft errors occur when incident radiation changes the electrical charge being held by a storage element, thereby changing its binary state. As the statistical significance of soft errors has been increasing, storage structures such as latches that were previously less prone to soft errors are now in need of protection.
Soft errors, if undetected, can silently corrupt data for a program during its execution. If the program continues to execute, incorrect results may be generated. This type of silent data corruption (SDC) is especially undesirable in mission critical applications, such as for commercial transaction server applications, where wrong results can have broad reaching implications.